class D{

}
public class test5 {
    //使用两个线程来累加 count 的值
    //每个线程循环 1w 次，累加变量 count 的值，count 默认值为 0，注意线程安全问题。
    private static int count=0;
    public static void main(String[] args) throws InterruptedException{
        Thread t1=new Thread(()->{
            synchronized (D.class) {
                for (int i = 0; i < 10000; i++) {
                    count++;
                }
            }
        });
        Thread t2=new Thread(()->{
            synchronized (D.class) {
                for (int i = 0; i < 10000; i++) {
                    count++;
                }
            }
        });
        t1.start();
        t2.start();
        t1.join();
        t2.join();
        System.out.println(count);
    }
}
